[Multiple Datasource][Meta] Feature GA in 2.7 release

[zhongnansu]

Multiple Datasource was first released in 2.4 as an experimental feature. This is the meta issue to track all the items we'll deliver to bring Multiple Datasource out of experimental, targeting 2.7 release.

• Feature: Integrate Multiple Datasource with dev tool console
  • prerequisite: Replace http client with opensearch-js client in dev tool console #3546
  • [MD]Multi data source integration with Dev tool #2699
  • must have bug fix: [BUG] custom error not display correctly after dev tool console refactoring #3645
  • good to have bug fix: [BUG] Dev tool console autocomplete suggestion doesn't suggest index name #3515
• Feature: Enable users to create index patterns for indices with same name but from different datasources
  • [MD] Allow create index patterns for indices with same name but from different datasources. #2597
  • Prepend <datasource-name>. to index pattern name to differentiate across data sources #2599
• UI/UX refactor
  • [Multiple Datasource] Convert authentication method from radio button to dropdown list #3551
  • [Multiple Datasource]Remove experiment feature banner.  #3579
  • [Console][Multiple Datasource]Fine tuned dev tool datasource selector UI #3806

[zhongnansu]

All PRs are opened

[joshuarrrr]

All tasks completed